Method of producing electrostatically charged gelatin

ABSTRACT

Methods of forming electrostatically charged gelatin are provided. Gelatin is extracted by an acid extraction method ( 12 ) thereby producing a gelatin dispersion ( 14 ), the pH of which is adjusted to the isoelectric point of the gelatin. The pH of the gelatin dispersion ( 14 ) is then further adjusted ( 22 ) so as to cause the gelatin to assume an electrostatic charge.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally concerns methods of formingelectrostatically charged gelatin. More specifically, the inventionpertains to methods whereby gelatin is extracted from acollagen-containing raw material and processed so as to produce agelatin product exhibiting an overall positive or negative electrostaticcharge based upon the particular processing conditions employed.

[0003] 2. Description of the Prior Art

[0004] Gelatin is a transparent, brittle, essentially odorless andtasteless powder. Gelatin is typically extracted from by-products of themeat industry including pork skin, tendons, ligaments, and bones.Gelatin has been utilized in numerous applications because of itsability to absorb 5-10 times its own weight in water and to form a gelin solutions having temperatures of about 35-40° F. and below. Gelatinhas been used in the manufacture of rubber substitutes, adhesives,cements, lithographic and printing inks, plastic compounds, artificialsilk, photographic plates and films, matches, light filters for mercurylamps, clarifying agents, hectographic masters, sizing paper, andtextiles. The pharmaceutical industry has utilized gelatin as asuspending agent, an encapsulating agent, a tablet binder, and a coatingagent.

[0005] Gelatin has been used in the food industry as a thickener, a foodstabilizer and a food texture enhancer. However, the use of gelatin inthe pet food industry has been rare due in part to its expense and theavailability of less costly viscosity enhancing agents such as gumsderived from plant and vegetable sources. Generally, in food industryapplications, gelatin exhibits no net electrostatic charge. Theconventional method of extracting food-grade gelatin includes adjustingthe pH of the gelatin-containing aqueous dispersion to the isoelectricpoint of the gelatin. The isoelectric point is the pH at which amaterial exhibits no net electrostatic charge.

[0006] In some food-related applications, it may be desirable to useelectrostatically charged gelatin. For example, gelatin having anegative electrostatic charge may be incorporated intohairball-prevention pet food products. In the formation of a hairball,the hair ingested by the animal clings to the lining of the stomachwhere it becomes entangled with other hairs and undigested food.Hairballs can be very problematic for the animal in that hairballs canlead to diarrhea and vomiting. If the animal were to ingest gelatinhaving a negative electrostatic charge, the gelatin would attract thehair inside the stomach of the animal and carry it through the animal'sdigestive system thereby preventing hairball formation.

[0007] U.S. Pat. No. 2,398,004 teaches a method of controlling theisoelectric point of gelatin for use in photographic applications. Theisoelectric point of the gelatin may be altered by the addition of analkali to increase the pH of the gelatin solution. This pH is maintainedfor a period of time and subsequently, the action of the alkali isstopped by the addition of an acid.

[0008] U.S. Pat. No. 2,514,635 discloses a method of reducing theviscosity of gelatin, especially photographic gelatin. The method usesan amine and amine salt buffer to raise the pH of the gelatin solutionin order to increase the gelatin viscosity.

[0009] No method of manufacturing gelatin has thus far been availablewhich would enable the gelatin to assume an electrostatic charge.Therefore, there exists a real and unfulfilled need for a method ofproducing gelatin having an electrostatic charge and being of food-gradequality.

SUMMARY OF THE INVENTION

[0010] The present invention overcomes the above problems and providesmethods of forming electrostatically charged gelatin. In a preferredembodiment, a collagen-containing raw material is provided and formedinto an aqueous slurry. A gelatin dispersion is formed by extractinggelatin from the slurry at a pH of from about 2-3. A first pH adjustmentstep is performed whereby the pH of the gelatin dispersion is adjustedto the isoelectric point of the gelatin. Preferably, the gelatin has anisoelectric point of from about 4.5-5.5 and more preferably about 4.6.Non-gelatin impurities are removed from the gelatin dispersion and thepH adjusted a second time in order to cause the gelatin to assume anelectrostatic charge.

[0011] The step whereby non-gelatin impurities are removed from thegelatin dispersion generally comprises filtering the gelatin dispersion.Preferably, the gelatin dispersion undergoes a first filtration step forremoval of insoluble materials such as hair and bone which may have beena part of the collagen-containing raw material from which the initialslurry was formed and the gelatin extracted. After the first filtration,the gelatin dispersion undergoes a second filtration or“ultrafiltration” whereby various non-gelatin protein impurities areremoved.

[0012] In another preferred embodiment, electrostatically chargedgelatin is formed by providing a collagen-containing raw material andforming the raw material into an aqueous slurry. A gelatin dispersion isformed by extracting gelatin from the slurry. During a first pHadjustment step, the pH of the gelatin dispersion is adjusted to theisoelectric point of the gelatin. A second pH adjustment of the gelatindispersion is performed causing the gelatin to assume an electrostaticcharge.

[0013] Following the second pH adjustment step, the gelatin dispersionis further purified by removing or neutralizing trace amounts of chargedimpurities. A preferred method of removing charged impurities such asminerals, ions, and peptides involves passing the gelatin dispersionthrough either a cation or anion column. If the gelatin is negativelycharged, the dispersion is passed through an anion column wherebypositively charged impurities are removed. If the gelatin is positivelycharged, the dispersion is passed through a cation column wherebynegatively charged impurities are removed.

[0014] Preferably, following passage through the anion or cation column,the electrostatic charge of the gelatin is enhanced by passing a DCelectric current through the gelatin dispersion. This enhancementoperation enhances the overall electrostatic charge of the gelatin byadding or removing electrons from the gelatin, whichever the case maybe. Preferably, the DC electric current, has a voltage of from about1-100 mV, more preferably from about 5-50 mV and most preferably about10 mV. The DC current preferably has an amperage of about 1-10 A, morepreferably about 2-4 A, and most preferably about 2 A. Preferably, thecurrent is passed through the gelatin dispersion for a period of up toabout 45 seconds, more preferably from about 10-40 seconds, and mostpreferably from about 10-15 seconds. If the gelatin is negativelycharged, a negative DC current is passed through the dispersion therebyenhancing the negative charge of the gelatin. If the gelatin ispositively charged, a positive DC current is passed through thedispersion thereby enhancing the positive charge of the gelatin.

[0015] In yet another preferred embodiment, previously isolated gelatin,that is, gelatin which has been previously extracted and dried into apowder, is formed into an aqueous dispersion. The pH of the gelatindispersion is adjusted thereby causing the gelatin to assume anelectrostatic charge. Moisture is then removed from the gelatindispersion forming a gelatin concentrate without first neutralizing thegelatin dispersion, that is, the acid or base used to make the pHadjustment is not neutralized prior to moisture removal.

[0016] Preferably, once moisture has been removed from the gelatindispersion, the gelatin concentrate undergoes a sterilization processthereby making the gelatin suitable for use in food products. Thegelatin concentrate may be sterilized using any method known to thoseskilled in the art, however it is preferable to employ a heatsterilization process using superheated steam at a temperature of fromabout 250°-350° F., more preferably from about 300°-330° F., and mostpreferably at about 310°-315° F. During the heat sterilization process,the gelatin concentrate is exposed to the superheated steam for about2-10 seconds.

[0017] The pH adjustment step causing the gelatin to assume a negativeelectrostatic charge comprises adjusting the pH of the gelatindispersion to between about 9-13, more preferably to between about10-12, and most preferably to between about 11-12. The pH adjustmentstep causing the gelatin to assume a positive electrostatic chargecomprises adjusting the pH of the gelatin dispersion to between about1-4, more preferably to between about 1.5-4, and most preferably tobetween about 2-3. The pH adjustments may be performed by adding to thegelatin dispersion acidic and basic materials known to those skilled inthe art. Preferred acids include organic acids such as acetic acid,citric acid, malic acid, fumaric acid, lactic acid and inorganic acidssuch as sulfuric acid and phosphoric acid. Sulfuric acid is the mostpreferred acid for lowering the pH of the gelatin dispersion. Preferredbases include alkali and alkaline earth metal carbonates such as sodiumcarbonate, potassium carbonate, calcium carbonate and alkali andalkaline earth metal hydroxides such as potassium hydroxide and sodiumhydroxide. Sodium hydroxide is preferred for raising the pH of thegelatin dispersion.

[0018] Once the gelatin has assumed an electrostatic charge and aportion of the gelatin solution moisture has been removed, the gelatinconcentrate preferably undergoes a drying process to form a gelatinpowder. Any drying process known to those of skill in the art may beused in forming the gelatin powder; however, spray drying and vacuumtray drying are preferred. During the drying process, the moisturecontent of the gelatin is reduced to between about 6-12% by weight, morepreferably to between 10-12% by weight, and most preferably to about12.0% by weight.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 depicts a prior art process of gelatin extraction wherebyelectrostatically neutral gelatin is formed.

[0020]FIG. 2 is depicts a process according to the present inventionwhereby electrostatically charged gelatin is formed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0021] Pure gelatin is composition comprising a plurality of amino acidsin varying amounts. Table 1 illustrates preferred gelatin compositionsfor use with the present invention. Amounts of each amino acid are givenin the form of a preferred range. TABLE 1 Amino acid Amount (by weight)Glycine 25.50-30.50% Proline 16.20-18.00% Hydroxyproline 13.50-14.50%Glutamic acid 11.00-11.70% Alanine  8.60-11.0% Arginine  8.10-9.10%Aspartic acid  6.20-6.90% Lysine  4.10-5.20% Valine  2.50-3.40%Phenylalanine  2.10-2.50% Leucine  3.10-3.40% Threonine  1.90-2.20%Isoleucien  1.36-1.80% Methionine  0.80-1.00% Histidine  0.74-1.00%Tyrosine  0.20-1.00% Serine  2.90-4.20% Cystine  0.05-0.10% Cysteine 0.05-0.10%

[0022] While not wishing to be, bound by any particular theory, it isbelieved that the imposition an electrostatic charge on the gelatininvolves either the addition or removal of electrons from various groupson at least one of the amino acids which comprise gelatin. If thegelatin is to have a negative electrostatic charge, an electron is addedto the carboxyl group of an amino acid while the amino group remainsneutral. If the gelatin is to have a positive electrostatic charge, anelectron is removed from the amino group of the amino acid while thecarboxyl group remains neutral.

[0023]FIG. 1 depicts a prior art process for producing electricallyneutral gelatin. Collagen-containing raw material, typically meatindustry by-products, is supplied by a tanker truck 10. The raw materialis ground into small particles and fed to an acidic gelatin extractionprocess 12. During the gelatin extraction process 12, gelatin isextracted from the collagen-containing raw material and a gelatindispersion 14 is formed. The pH of gelatin dispersion 14 is adjusted to4.6 and then sent to a filtering process 16 whereby impurities areremoved. The filtered gelatin dispersion 18 is sent to a dryingoperation where moisture is removed and a gelatin powder 20 is formed.

[0024]FIG. 2 depicts a preferred method of forming electrostaticallycharged gelatin according to the present invention. Collagen-containingraw material is supplied by tanker truck 22. The raw material is groundinto small particles and fed to an acidic gelatin extraction process 24.Water is added to the raw materials to form a slurry and the pH of theslurry is adjusted to about 2.0-3.0 using sulfuric acid. The slurry ismaintained in this pH range for a period of up to 4 days at which timethe slurry undergoes a series of heating steps and the gelatin isextracted forming a gelatin dispersion 26. The heating steps occur overa 3 hour period whereby the slurry is heated a plurality of times totemperatures of at least 140° F. Following the heating steps, the pH ofthe slurry is adjusted to 4.6, the isoelectric point of the gelatin, bythe addition of sodium hydroxide. At this point, the gelatin bears noelectrostatic charge.

[0025] The gelatin dispersion 26 then undergoes a filtration operation28 where impurities are removed. The filtration operation 28 occurs intwo stages, the first of which involves removing insoluble materialssuch as hair and bone which were introduced into the process with theraw materials. The second filtration stage is an “ultrafiltration” stagewhereby very fine particles including non-gelatin proteins are removedfrom the gelatin dispersion 26.

[0026] Depending on the electrostatic charge desired, the remainder ofthe process proceeds in one of two directions. If gelatin with anegative electrostatic charge is desired, the pH of dispersion 30 isadjusted by the addition of sodium hydroxide 32 a to between about10-12. This pH adjustment step causes the carboxyl group of at least oneof the amino acids from which gelatin is comprised to assume a negativecharge. However, the amino group of the amino acid remainselectrostatically neutral. Therefore, the gelatin assumes an overallnegative electrostatic charge.

[0027] After the pH adjustment step, the negatively charged gelatindispersion 34 a undergoes a purification step 36 a in order to remove orneutralize trace amounts of positively charged minerals, ions orpeptides. Purification step 36 a comprises passing negatively chargedgelatin dispersion 34 a through an anion column whereby the positivelycharged impurities are removed from dispersion 34 a. Following thepurification step, the negative electrostatic charge of the gelatin isenhanced by passing a negative DC current through the dispersion 34 a.The negative DC current has a voltage of about 10 mV and an amperage ofabout 2 A and is passed through dispersion 34 a for a period of about 10seconds.

[0028] The enhanced gelatin dispersion 38 a is finally sent to amoisture removal and drying operation 40 a wherein a powdered,electrostatically charged gelatin product of food grade quality isformed. Operation 40 a first comprises the evaporation of a portion ofthe moisture of enhanced dispersion 38 a under a vacuum thereby forminga gelatin concentrate. The concentrate is sterilized by exposure tosuperheated steam for not more than 10 seconds and then dried into apowder having a moisture content of about 12% by weight using a hot airspray dryer.

[0029] Alternatively, if gelatin with a positive electrostatic charge isdesired, the pH of dispersion 18 is adjusted by the addition ofphosphoric acid 32 b to between about 2-3. This pH adjustment stepcauses the amino group of at least one of the amino acids from whichgelatin is comprised to assume a positive charge. However, the carboxylgroup of the amino acid remains electrostatically neutral. Therefore,the gelatin assumes an overall positive electrostatic charge.

[0030] After the pH adjustment step, the positively charged gelatindispersion 34 b undergoes a purification step 36 b in order to remove orneutralize trace amounts of negatively charged minerals, ions orpeptides. Purification step 36 b comprises passing positively chargedgelatin dispersion 34 b through a cation column whereby the negativelycharged impurities are removed from dispersion 34 b. Following thepurification step, the positive electrostatic charge of the gelatin isenhanced by passing a positive DC current through the dispersion 34 a.The positive DC current has a voltage of about 10 mV and an amperage ofabout 2 A and is passed through dispersion 34 b for a period of about 10seconds.

[0031] The enhanced gelatin dispersion 38 b is finally sent to amoisture removal and drying operation 40 b wherein a powdered gelatinproduct of food grade quality is formed. Operation 40 b first comprisesthe evaporation of a portion of the moisture of enhanced dispersion 38 bunder a vacuum thereby forming a gelatin concentrate. The concentrate issterilized by exposure to superheated steam for not more than 10 secondsand then dried into a powder having a moisture content of about 12% byweight using a vacuum tray dryer. In this instance, a vacuum tray drieris preferred to a hot air spray drier because hot air drying mayadversely affect the positive charge of the gelatin thereby having aneutralizing effect.

EXAMPLES

[0032] The following examples set forth preferred methods in accordancewith the present invention. It is to be understood, however, that theseexamples are provided by way of illustration and nothing therein shouldbe taken as a limitation upon the overall scope of the invention.

Example 1

[0033] In this example, gelatin having a negative electrostatic chargeis extracted from pigskin. Approximately 4,000 lbs. of pigskin is groundto a particle size of less than about 1.5 mm using a {fraction (1/16)}in. plate. The ground pigskin is then mixed with water to form a slurry.The pH of the slurry is adjusted to 2.5 using sulfuric acid. The slurryis maintained under acidic conditions for up to 4 days. The slurry thenundergoes three heating steps whereby the gelatin is extracted. Eachheating step lasts about 60 minutes. The first extraction step involvesheating the slurry to 145° F., the second to 165° F., and the third to185° F. The heat denaturing of the collagen contained in the pigskinresults in the unwinding of the polypeptide chains thereby releasing thegelatin.

[0034] After the gelatin is extracted, the pH of the gelatin dispersionis adjusted to 4.6, the isoelectric point of the gelatin, by theaddition of sodium hydroxide. The gelatin dispersion is then filtered toremove suspended solid residues and then filtered again to removeprotein impurities from the gelatin dispersion. Following the filtrationsteps, the pH of the gelatin dispersion is adjusted to 12 using sodiumhydroxide.

[0035] The gelatin dispersion is passed through an anion column toremove trace amounts of positively charged minerals, ions, and peptides.Upon leaving the anion column, the dispersion is sent to an evaporationprocess operating under a vacuum thereby forming a gelatin concentratewhich comprises 30% gelatin. The gelatin concentrate is sterilized byexposing the concentrate to superheated steam at a temperature of 315°F. for 5 seconds. Once sterilized, the gelatin concentrate is spraydried at a temperature of 346° F. thereby recovering the gelatin inpowder form. This process yields approximately 680 lbs. of gelatinhaving a negative electrostatic charge.

Example 2

[0036] In this example, gelatin having a positive electrostatic chargeis extracted from pigskin. The pigskin is initially treated as describedin Example 1 through the gelatin extraction and filtration stages. Afterfiltration of the gelatin dispersion, the pH of the dispersion isadjusted to 2.5 using phosphoric acid. The gelatin dispersion is thenpassed through a cation column to remove trace amounts of negativelycharged minerals, ions and peptides. After leaving the cation column,the gelatin is processed into powder form as in Example 1, with theexception that the gelatin concentrate is vacuum oven dried as opposedto spray dried. This process yields approximately 740 lbs. of gelatinhaving a positive electrostatic charge.

Example 3

[0037] In this example, gelatin having a negative electrostatic chargeis extracted from pigskin. The process of this example is the same asthat of Example 1 and includes the additional step of enhancing thegelatin's overall negative charge by passing a negative DC currentthrough the gelatin dispersion after impurity removal in the anioncolumn. A negative DC current at 10 mV and 2 A is passed through thegelatin dispersion for 10 seconds. The gelatin dispersion is thenconcentrated, sterilized and spray dried as in Example 1. This processyields about 650 lbs. of gelatin having a negative electrostatic charge.

Example 4

[0038] In this example, gelatin having a positive electrostatic chargeis extracted from pigskin. The process of this example is the same asthat of Example 2 and includes the additional step of enhancing thegelatin's overall positive charge by passing a positive DC currentthrough the gelatin dispersion after impurity removal in the anioncolumn. A positive DC current at 15 mV and 2 A is passed through thegelatin dispersion for 15 seconds. The gelatin dispersion is thenconcentrated, sterilized and vacuum oven dried as in Example 2. Thisprocess yields about 700 lbs. of gelatin having a positive electrostaticcharge.

We claim:
 1. A method of forming electrostatically charged gelatincomprising the steps of: providing a collagen-containing raw material;forming an aqueous slurry with said raw material; forming a gelatindispersion by extracting gelatin from said slurry at a pH of from about2-3; performing a first pH adjustment whereby the pH of said gelatindispersion is adjusted to the isoelectric point of said gelatin;removing non-gelatin impurities from said gelatin dispersion; andperforming a second pH adjustment whereby the pH of said gelatindispersion is adjusted causing said gelatin to assume an electrostaticcharge.
 2. The method of claim 1, said second pH adjustment stepcomprising adjusting the pH of said gelatin dispersion thereby causingsaid gelatin to assume a negative electrostatic charge.
 3. The method ofclaim 2, said second pH adjustment step comprising adjusting the pH ofsaid gelatin dispersion to between about 10-12.
 4. The method of claim1, said second pH adjustment step comprising adjusting the pH of saidgelatin dispersion thereby causing said gelatin to assume a positiveelectrostatic charge.
 5. The method of claim 4, said second pHadjustment step comprising adjusting the pH of said gelatin dispersionto between about 2-3.
 6. The method of claim 1, the isoelectric point ofsaid gelatin being from about 4.5-5.5.
 7. The method of claim 1, furthercomprising the step of passing a DC electric current through saidgelatin dispersion.
 8. The method of claim 1, further comprising thestep of removing moisture from said gelatin dispersion thereby forming agelatin concentrate.
 9. The method of claim 8, further comprising thestep of sterilizing said gelatin concentrate.
 10. The method of claim 1,further comprising the step of spray drying said gelatin dispersion. 11.The method of claim 1, said impurities removal step comprising filteringsaid gelatin dispersion.
 12. The method of claim 11, said filtering stepcomprising a first filtration whereby insoluble materials are removedfrom said gelatin dispersion, and a second filtration wherebynon-gelatin proteins are removed from said gelatin dispersion.
 13. Amethod of forming electrostatically charged gelatin comprising the stepsof: providing a collagen-containing raw material; forming an aqueousslurry with said raw material; forming a gelatin dispersion byextracting gelatin from said slurry; performing a first pH adjustmentwhereby the pH of said gelatin dispersion is adjusted to the isoelectricpoint of said gelatin; performing a second pH adjustment whereby the pHof said gelatin dispersion is adjusted causing said gelatin to assume anelectrostatic charge; and applying a DC electric current to said gelatindispersion.
 14. The method of claim 13, said second pH adjustment stepcomprising adjusting the pH of said gelatin dispersion thereby causingsaid gelatin to assume a negative electrostatic charge.
 15. The methodof claim 14, said second pH adjustment step comprising adjusting the pHof said gelatin dispersion to between about 10-12.
 16. The method ofclaim 13, said second pH adjustment step comprising adjusting the pH ofsaid gelatin dispersion thereby causing said gelatin to assume apositive electrostatic charge.
 17. The method of claim 16, said secondpH adjustment step comprising adjusting the pH of said gelatindispersion to between about 2-3.
 18. The method of claim 13, theisoelectric point of said gelatin being from about 4.5-5.5.
 19. Themethod of claim 13, applying a positive DC electric current to saidgelatin dispersion.
 20. The method of claim 13, applying a negative DCelectric current to said gelatin dispersion.
 21. The method of claim 13,further comprising the step of removing moisture from said gelatindispersion thereby forming a gelatin concentrate.
 22. The method ofclaim 21, further comprising the step of sterilizing said gelatinconcentrate.
 23. The method of claim 13, further comprising the step ofspray drying said gelatin dispersion.
 24. A method of formingelectrostatically charged gelatin comprising the steps of: forming anaqueous dispersion with previously isolated gelatin; adjusting the pH ofsaid gelatin dispersion causing said gelatin to assume an electrostaticcharge; removing moisture from said gelatin dispersion thereby forming agelatin concentrate without first neutralizing said dispersion.
 25. Themethod of claim 24, said pH adjustment step comprising adjusting the pHof said gelatin dispersion thereby causing said gelatin to assume anegative electrostatic charge.
 26. The method of claim 25, said pHadjustment step comprising adjusting the pH of said gelatin dispersionto between about 10-12.
 27. The method of claim 24, said pH adjustmentstep comprising adjusting the pH of said gelatin dispersion therebycausing said gelatin to assume a positive electrostatic charge.
 28. Themethod of claim 27, said pH adjustment step comprising adjusting the pHof said gelatin dispersion to between about 2-3.
 29. The method of claim24, further comprising the step of passing a DC electric current throughsaid gelatin dispersion.
 30. The method of claim 24, further comprisingthe step of sterilizing said gelatin concentrate.